Immunological features of oligomenorrhea in adolescent girls with excess weight

Introduction

In recent years, the prevalence of childhood obesity has increased, which is a disease with serious consequences for physiological and metabolic body functions [1]. It has been established that overweight and obesity in adolescence predispose individuals to insulin resistance (IR) and type 2 diabetes, hypertension, hyperlipidemia, liver and kidney diseases, and ovarian dysfunction [2][3]. Adipose tissue takes part in the exchange of sex hormones and estrogen synthesis, the consequence of which is dysregulation of hormonal balance. Overweight increases the content of leptin and adiponectin, which are critical in menstrual regulation. On the other hand, there is a strong relationship between obesity and increased levels of inflammatory cytokines in the blood serum involved in attracting and activating macrophages, which may be the trigger for metabolic homeostasis disorder and ovarian dysfunction [4]. Therefore, studying the immunological features of oligomenorrhea in overweight girls is timely and relevant.

The aim of the study is to identify the immunological features of oligomenorrhea in overweight adolescent girls.

Materials and methods

The object of the study was presented by 80 adolescent girls with overweight and oligomenorrhea, included in group I, and 64 obese adolescent girls without cycle disorders, included in group II. The control group included 25 healthy adolescent girls. Leptin, sR-leptin, IL-6, TNF-α, and sTNF-αR1 were determined by an enzyme-linked immunosorbent assay (BenderMedSystems). Expression of TLR-2 and TLR-4 was analyzed by flow cytometry (HyCultbiotechnology). An analysis of the nucleotide polymorphism Asp299Gly of the TLR-4 gene was carried out by PCR using a standard set from the State Research Institute of Genetics (Russia). Descriptive statistics were performed using the Mann-Whitney test, with an error of the first kind p<0.05. To study the frequency of allele and genotype polymorphism by a binary trait, the χ² criterion was used.

Results

Leptin, synthesized by fat cells, promotes the transition from carbohydrate oxidation to fat oxidation and regulates glucose homeostasis [5]. The analysis data established increased leptin production in overweight patients, both with and without cycle abnormalities. Interestingly, the highest leptin level was determined in girls with oligomenorrhea (Table 1).

The analysis data showed that the blood serum level of soluble leptin receptors in obese girls with oligomenorrhea was statistically significantly lower than in group II and the control group (Table 1).

TNF-α plays a significant role in many biological processes, such as immunomodulation and inhibition of viral replication, and supports inflammation processes in adipose tissue, contributing to metabolic disorders [6][7]. The mean blood serum TNF-α level was increased in patients of the study groups, but significant differences with the control group were found only in patients with oligomenorrhea (Table 2).

The content of sR1-TNF-α in overweight patients without menstrual disorders exceeded its content in the control group and group I. The TNF-α/sR1-TNF-α index study showed the highest results in patients with overweight and oligomenorrhea (Table 2).

Interleukin 6 (IL-6) has regulatory functions in maintaining homeostasis of the body’s main systems such as the nervous and immune systems, and also plays a significant role in ovarian dysfunction and metabolic dysfunctions [8].

The analysis data demonstrated an increase in the IL-6 level in overweight patients. The most pronounced shifts were noted in group I (Table 2). This fragment of studies makes it possible to conclude that the development of oligomenorrhea in adolescent girls against the background of obesity is associated with an increase in the level of adipocytokine-leptin, TNF-α, and IL-6, leading to IR.

Recognition of molecular patterns associated with the pathogen and endogenous ligands induces expression of TLR [9][10]. High expression of TLR-2 (CD14+CD282+) was observed in patients of group I compared to patients of the control group and group II (p<0.05). In both clinical groups, an increase in the expression of TLR-4 (CD14+CD284+) was observed (p<0.05). Inflammation and IR in obesity are associated with menstrual disorders, so genetic variations in TLR can be involved in the interaction between overweight and oligomenorrhea. When studying the genotypes and alleles Asp299Gly of the TLR-4 gene, it was found that the Asp/Asp genotype, as well as the Asp allele, were less common in group I compared to the healthy control group and group II (p<0.05).

Discussion

The health of adolescent girls is one of the main components of the reproductive health of the nation, determining the future demographic situation in the country. The relevance of studying the factors affecting the formation of reproductive pathology in overweight adolescent girls is due to the increase in gynecological morbidity among this contingent of patients. The immune system and metabolic regulation are tightly integrated, and their functions are interdependent. This interface can be considered a central homeostatic mechanism, the dysfunction of which can lead to both inflammation processes and metabolic disorders, in particular, obesity. Inflammation accompanying metabolic syndrome inhibits insulin sensitivity through the activation of signaling pathways that directly affect insulin signaling pathways.

In obesity, the secretion pattern of adipocytokines undergoes significant changes. Leptin is a “signaling” protein of homeostasis; it regulates the processes of fat metabolism and is involved in maintaining the hormonal immunological balance. Abnormal leptin levels can lead to various endocrine and metabolic disorders, as well as ovarian failure. Our findings on increased leptin levels in overweight patients are consistent with [11] that hyperleptinemia can contribute to a chronic inflammatory response, which, in turn, can disrupt leptin functions, causing leptin resistance, due to a violation of the feedback mechanism in the “leptin-receptor” system.

A decrease in the level of soluble leptin receptors in patients with overweight and cycle disturbance revealed in the work indicates that this circumstance is of great importance in the development of oligomenorrhea. Our data do not contradict the results of work [12], which indicated that a decrease in the amount of soluble leptin receptor, depending on the degree of abdominal obesity, can cause the progression of leptin resistance in patients with metabolic syndrome.

It should also be noted that data on the content of leptin and its soluble receptors in adolescent girls are practically absent in the scientific literature.

Under conditions of excess body weight, immune cells accumulate in adipose tissue, cytokines and chemokines are synthesized, which are involved in the regulation of metabolic cascades, are the main stimulators of the hypothalamic-pituitary-adrenal system, which leads to an increase in cortisol secretion. The action of proinflammatory cytokines can directly affect the development of IR, dyslipidemia, as well as endothelial activation, resulting in vasoconstriction and disorders of hemostasis, endothelial dysfunction, as an integral part of the chronic systemic inflammatory response.

TNF-α is one of the most important pro-inflammatory cytokines – mediators of IR. The increase in TNF-α levels in overweight patients identified in this study is consistent with the data of [13]; it can lead to impaired glucose homeostasis and insulin sensitivity. sR1-TNF-α by binding to transmembrane TNF-α blocks its function, and thus prevents the formation of IR in overweight patients without disrupting of the cycle. Inversion of the TNF-α /sR1-TNF-α index recorded by us can be considered as an indicator reflecting the role of production and biological activity of TNF-α in oligomenorrhea formation.

By a variety of cellular sources of production and targets of biological action, IL-6 is one of the most active cytokines involved in the implementation of the immune response and development of inflammatory reaction. An increase in the IL-6 level in patients of both clinical groups suggests that overweight potentiates IL-6 expression and can contribute to the formation of metabolic inflammation.

Obesity is characterized by chronic inflammation and activation of innate immunity, which leads to the induction of IR. The imbalance of innate immunity factors, in particular TLR, in obese adolescent girls remains poorly understood. The high level of TLR-2 and TLR-4 expression found by us can contribute to an increase in the synthesis of proinflammatory cytokines, the formation of IR, and ovarian dysfunction. The polymorphism of genes encoding TLR affects the efficiency of the immune response. The results suggest that genetic features, i.e. the presence of the Gly allele of the TLR-4 gene, are a predisposition factor to IR and oligomenorrhea in obese patients, and the presence of the Asp/Asp genotype is associated with a successful outcome of the disease.

Conclusion

There is a strong link between metabolic and immune responses. Inflammation caused by increased synthesis of proinflammatory cytokines is associated with metabolic disorders, dysregulation of carbohydrate and lipid metabolism. A reduction in the level of soluble leptin receptors can cause an increase in leptin resistance, forming a vicious circle, which increases the likelihood of obesity. These patients have an increase in the production of cytokine with pro-inflammatory activity. Allelic variants Asp299Gly of the TLR-4 gene can be risk factors for oligomenorrhea formation in overweight adolescent girls. The established immunological features potentiate dysfunction of the hypothalamic-pituitary-adrenal system, an increase in the level of male sex hormones, and ovarian dysfunction. The pathogenetic significance of immunity factors in oligomenorrhea genesis determines the necessity of continuing the work with this category of patients, which will contribute to the preservation of reproductive potential.